KR20160139256A - Catalyst layer for fuel cell, and membrane-electrode assembly for fuel cell and fuel cell including the same - Google Patents

Abstract

Provided are a catalytic layer for fuel cells, a membrane-electrode assembly for fuel cells including the same, and a fuel cell system. According to the present invention, the catalytic layer for fuel cells has an upper surface and a lower surface, and the upper surface includes a first region and a second region. The first region contains less amount of ionomer than the second region, and the content of the first region is 10-50% based on the total area of the upper surface.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst layer for a fuel cell, a membrane electrode assembly for a fuel cell,

A catalyst layer for a fuel cell, a membrane-electrode assembly for a fuel cell including the same, and a fuel cell.

A fuel cell is a power generation system that converts the chemical reaction energy of hydrogen and hydrogen gas contained in a hydrocarbon-based material such as methanol, ethanol, natural gas, etc. directly into electrical energy. This fuel cell is a clean energy source that can replace fossil energy. It has the advantage of being able to output a wide range of output by stacking the unit cells by stacking them. The fuel cell has an energy density of 4 to 10 times , It is attracting attention as a backup power source, a mobile power source, an industrial power source, and an automobile power source.

Representative examples of the fuel cell include a polymer electrolyte membrane fuel cell (PEMFC), a direct oxidation fuel cell, and the like. When methanol is used as the fuel in the direct oxidation fuel cell, it is referred to as a direct methanol fuel cell (DMFC). Direct oxidation fuel cells have lower energy density than polymer electrolyte fuel cells, but are easier to handle and operate at lower temperatures, and can be operated at room temperature. In particular, they do not require a fuel reformer. The polymer electrolyte fuel cell has advantages of high energy density and high output.

In this fuel cell system, the stack which substantially generates electricity has a structure in which several to ten unit cells are formed of a membrane-electrode assembly (MEA) and a separator. The membrane-electrode assembly is referred to as an anode electrode (also referred to as a "fuel electrode" or an "oxidizing electrode") and a cathode electrode (a so-called "air electrode" or a "reducing electrode") with a polymer electrolyte membrane containing a proton- ) Are located.

The principle of generating electricity in the fuel cell is that the fuel is supplied to the anode electrode as the fuel electrode and adsorbed on the catalyst of the anode electrode and the fuel is oxidized to generate hydrogen ions and electrons, And the hydrogen ions pass through the polymer electrolyte membrane and are transferred to the cathode electrode. The oxidant is supplied to the cathode electrode, and the oxidant, the hydrogen ion and the electrons react with each other on the catalyst of the cathode electrode to generate electricity while generating water.

Meanwhile, in order to secure the performance of the fuel cell, various functions such as fuel supply, water discharge, and hydrogen ion transfer should be performed well. However, these functions have trade-off characteristics,

One embodiment provides a catalyst layer for a fuel cell capable of improving cell performance by simultaneously performing various functions such as smooth supply of fuel, discharge of water, and hydrogen ion transfer.

Another embodiment provides a membrane-electrode assembly for a fuel cell comprising the catalyst layer.

Another embodiment provides a fuel cell comprising the membrane-electrode assembly.

An embodiment includes a top surface and a bottom surface, wherein the top surface includes a first region and a second region, wherein the first region has a lower ionomer content than the second region, To 10% to 50% of the total area of the catalyst layer.

The first region may have an ionomer content 2 to 10 times less than the second region.

The first region may be porous.

The first region may have a porosity of 30% by volume to 70% by volume.

The first region and the second region may have a height difference from the lower surface, and the height difference may be from 1.0 mu m to 3.0 mu m.

The first region may be located higher than the second region from the lower surface.

Another embodiment includes a cathode electrode and an anode electrode positioned opposite to each other; And a polymer electrolyte membrane interposed between the cathode electrode and the anode electrode, wherein the cathode electrode and the anode electrode each comprise an electrode substrate and a membrane electrode assembly for a fuel cell disposed on the electrode substrate and including the catalyst layer do.

According to another embodiment of the present invention, there is provided a fuel supply system comprising: a fuel supply unit for supplying a mixed fuel in which fuel and water are mixed; A reforming unit for reforming the mixed fuel to generate a reformed gas containing hydrogen gas; A stack including a membrane electrode assembly and a separator positioned on both sides of the membrane electrode assembly, wherein the reforming gas containing hydrogen gas supplied from the reformer causes an electrochemical reaction with the oxidant to generate electrical energy; And an oxidant supply part for supplying the oxidant to the reforming part and the stack.

Other details of the embodiments of the present invention are included in the following detailed description.

The performance of the fuel cell can be realized by simultaneously performing various functions such as smooth supply of fuel, discharge of water, and hydrogen ion transfer.

1 is a cross-sectional view of a catalyst layer for a fuel cell according to one embodiment.
2 is a plan view showing a surface of a catalyst layer for a fuel cell according to one embodiment.
FIG. 3 is a schematic view sequentially illustrating a process of forming a catalyst layer according to an embodiment. Referring to FIG.
4 is a schematic view showing a membrane-electrode assembly (MEA) for a fuel cell according to one embodiment.
5 is a schematic view showing the overall configuration of a fuel cell according to one embodiment.
6 is an exploded perspective view showing a stack of fuel cells according to one embodiment.
7A and 7B are scanning electron microscope (SEM) photographs of a catalyst layer according to Comparative Example 1 and Example 1, respectively, viewed from above, showing a magnification of 500. FIG.
8A and 8B are scanning electron microscope (SEM) photographs showing side surfaces of the catalyst layers according to Comparative Examples 1 and 1, respectively.
FIGS. 9A and 9B are scanning electron microscope (SEM) photographs showing the height difference on the side of the catalyst layer according to Comparative Example 1 and Example 1, respectively.
10 is a scanning electron microscope (SEM) photograph of the catalyst layer according to Example 1 taken from above and showing a magnification of 10,000.
11A and 11B are scanning electron microscope (SEM) photographs of the catalyst layers disassembled after evaluation of anode and cathode electrodes, respectively, according to Example 1. Fig.
12 is a graph showing the results of performance evaluation of the fuel cell according to Example 1 and Comparative Example 1. Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

It is to be understood that where a layer, film, region, plate, or the like is referred to as being "on" another portion, unless stated otherwise in this specification, .

The catalyst layer for a fuel cell mainly comprises a catalyst and an ionomer. Such a catalyst layer can secure the performance of a fuel cell by performing various functions such as a smooth supply function of fuel, a discharge function of water, a transfer function of hydrogen ion, and an electron transfer function. However, since the above functions have trade off characteristics, it is difficult to perform various functions simultaneously in the conventional catalyst layer. For example, if the amount of the ionomer is increased to smooth the transfer of the hydrogen ions, the supply of the fuel can not be smoothly performed. If the porous structure is formed for discharging water, the ionomer coverage is insufficient, It does not work smoothly.

According to one embodiment, the surface of the catalyst layer is divided into different different regions to texture the regions so that different regions perform different functions. Accordingly, the catalyst layer having a textured surface can smoothly perform various functions of smooth fuel supply, water discharge, hydrogen ion transfer, and electron transfer at the same time. When such a catalyst layer is applied to a fuel cell, .

Hereinafter, a catalyst layer for a fuel cell according to one embodiment will be described with reference to FIGS. 1 and 2. FIG.

1 is a cross-sectional view of a catalyst layer for a fuel cell according to one embodiment.

1, a catalyst layer 10 according to one embodiment has a bottom surface 12 and a top surface 14, the top surface including a first region A and a second region B . FIG. 1 is a reference for introducing the surface of the catalyst layer that is divided into different regions and textured, but the embodiment of the present invention is not limited thereto. That is, the number of area types shown in FIG. 1, the area of each area, the ratio of each area, the height of each area, the difference in height between the areas, and the like are only reference examples.

2 is a plan view showing a surface of a catalyst layer for a fuel cell according to one embodiment. In other words, FIG. 2 shows the structure when viewed from above the top surface 14 in FIG.

Referring to FIG. 2, the surface of the catalyst layer according to one embodiment, specifically, the upper surface 14 of the catalyst layer may include a first region A and a second region B. FIG. 2 is a view for helping explain the structure of the catalyst layer divided into different regions, and the embodiment of the present invention is not limited thereto. That is, the number of area types shown in FIG. 2, the area of each area, the ratio occupied by each area, and the like are merely a reference, and the embodiment of the present invention is not limited thereto.

The first region (A) may have a lower ionomer content than the second region (B). When the surface of the catalyst layer is formed into a textured structure by dividing the ionomer content into regions different from each other, different functions are assigned to each region even in one catalyst layer, so that various functions of fuel supply, water discharge, hydrogen ion transfer, Function can be performed simultaneously and smoothly in one catalyst layer. Specifically, in the first region where the ionomer content is relatively low, the fuel is supplied smoothly and the water is discharged. In the second region where the ionomer content is relatively large, the hydrogen ions are smoothly transferred, Several functions can be performed simultaneously and smoothly.

Specifically, the ionomer content of the first region may be 2 to 10 times, for example, 5 to 7 times smaller than that of the second region. When the ionomer content is varied within the above range, various functions such as smooth fuel supply, water discharge, hydrogen ion transfer, and electron transfer can be performed more smoothly at the same time, thereby ensuring a fuel cell having excellent battery performance.

The first region may be porous. Specifically, the first region may have a porosity of 30% by volume to 70% by volume, for example, a porosity of 40% by volume to 60% by volume. When the first region has the porosity within the above range, the fuel supply and the water discharge are smoothly performed, so that the function and the function in the second region can be achieved.

The first region may be contained in the catalyst layer in a proportion of 10% to 50% with respect to the total area of the surface of the catalyst layer, specifically, the total area of the first region and the second region. For example, % ≪ / RTI > to 40%. When the first region having a relatively small ionomer content is included in an area within the above range, it has an appropriate area ratio with the second region, so that various functions of fuel supply, water discharge, hydrogen ion transfer, Thus, a fuel cell having excellent cell performance can be realized.

The first region A and the second region B may have a height difference from the lower surface 12 of the catalyst layer. In other words, the portion of the catalyst layer having the first region and the portion of the catalyst layer having the second region in one catalyst layer may have different heights. This may be a structure in which the surface of the catalyst layer has a valley shape. When the first region and the second region having different ionomer contents have different heights, the surface area of the catalyst layer is increased to improve the battery performance, such as increasing the output density of the fuel cell.

Specifically, the height difference between the first region and the second region may be 1.0 탆 to 3.0 탆, and may be, for example, 1.5 탆 to 2.0 탆. When the height difference between the first region and the second region having different ionomer contents is within the above range, the surface area of the catalyst layer is increased, thereby improving the battery performance such as increasing the output density of the fuel cell.

More specifically, the first region having a relatively low ionomer content may be located at a higher position from the bottom surface than the second region. In other words, in the structure in which the surface of the catalyst layer has a valley shape, the top portion may be the first region, and the valley portion may be the second region.

The catalyst layer may comprise a catalyst and an ionomer.

The catalyst may be any catalyst that can be used as a catalyst in the reaction of the fuel cell. Specifically, a metal catalyst such as a platinum catalyst may be used.

As the platinum-based catalyst, platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, At least one transition metal selected from Cu, Zn, Sn, Mo, W, Rh and Ru).

In order to prevent the anode poisoning phenomenon due to carbon monoxide generated in the anode electrode reaction in the direct oxidation fuel cell, the anode electrode and the cathode electrode may be made of a platinum- Ruthenium alloy catalyst may be used.

The Pt / Ni / Pt / Mo / Pt / Pd / Pt / Fe / Pt / Cr / Pt / Co catalysts are examples of the platinum catalysts. At least one selected from Ru / W, Pt / Ru / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni and Pt / Ru / Sn /

The metal catalyst may be used as the metal catalyst itself or may be supported on a carrier. Examples of the carrier include carbonaceous materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, carbon nanowires, carbon nanoballs, and activated carbon, or alumina, silica, zirconia, Inorganic fine particles such as titania may be used. Of these, carbon-based materials are mainly used.

When a noble metal supported on the support is used as a catalyst, a commercially available commercially available noble metal may be used, or a noble metal may be supported on the support to be used. Since the process of supporting the noble metal on the carrier is well known in the art, a detailed description thereof is omitted herein, and it is easily understandable to those skilled in the art.

The ionomer may be used for improving adhesion of the catalyst layer and for transferring hydrogen ions.

The ionomer may be a polymer resin having hydrogen ion conductivity, specifically, a polymer resin having at least one cation-exchange group selected from a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group, Can be used. Specifically, a fluorine-based polymer, a benzimidazole-based polymer, a polyimide-based polymer, a polyetherimide-based polymer, a polyphenylene sulfide-based polymer, a polysulfone-based polymer, a polyether sulfone-based polymer, a polyether ketone- -Ether ketone-based polymer and polyphenylquinoxaline-based polymer may be used. For example, poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), copolymer of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid group, sulfated polyether ketone, aryl ketone, poly (2 , 2'-m-phenylene) -5,5'-bibenzimidazole and poly (2,5-benzimidazole) May be used.

In the polymer resin having hydrogen ion conductivity, H may be substituted with Na, K, Li, Cs or tetrabutylammonium in the cation exchanger at the side chain terminal. In the case of replacing H with Na in the ion exchange group at the side chain terminal, NaOH is substituted in the preparation of the catalyst composition and tetrabutylammonium hydroxide is used in the case of replacing with tetrabutylammonium, and K, Li or Cs is also substituted with a suitable compound . ≪ / RTI > Since this substitution method is well known in the art, a detailed description thereof will be omitted in this specification.

The ionomer may be used singly or in the form of a mixture, and may optionally be used together with a nonconductive compound for the purpose of further improving the adhesion with the polymer electrolyte membrane. The amount of the nonconductive compound to be used is preferably adjusted to suit the intended use.

Examples of the nonconductive compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoro (PVdF-HFP), dodecyltrimethoxysilane (DMSO), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer At least one selected from silbenzenesulfonic acid and sorbitol can be used.

The ionomer may be contained in an amount of 15 to 50% by weight based on the total amount of the catalyst layer, for example, 20 to 40% by weight. When the ionomer is contained within the above range, the adhesion of the catalyst layer is improved and the hydrogen ion transfer efficiency is increased.

Hereinafter, a method of manufacturing a catalyst layer according to one embodiment will be described with reference to FIG. FIG. 3 is a view for helping understanding of the method of manufacturing the catalyst layer, and the present invention is not limited to the catalyst layer structure shown in FIG. Also, FIG. 3 shows an example of a manufacturing method of a side layer according to one embodiment, and the manufacturing method of the catalyst layer is not limited thereto.

The catalyst layer having the above-described surface structure can be produced by the following method.

First, (a) a base film is prepared. The base film may be made of a material having poor compatibility with the ionomer which is the catalyst layer material to be formed. Examples thereof include polyimide films and polyethylene terephthalate films .

Next, (b) a coating layer is formed on the base film. The coating layer formation process is performed to form the texture structure of the surface of the catalyst layer. The coating layer may be made of a material having good affinity with the ionomer which is the catalyst layer material to be formed. For example, a fluorine-based polymer, a silicon-based polymer, and the like can be enumerated, and the fluorine-based polymer may include fluorinated ethylene propylene (FEP) and the like, but is not limited thereto. The coating method may be a wet method or the like, but is not limited thereto. Specifically, the coating layer can be formed with a texture structure having a valley shape by adjusting the thickness and the material concentration using a wet method. The thickness of the coating layer can be adjusted within a range of, for example, 5 탆 to 50 탆, and the concentration of the material can be adjusted within a range of, for example, 5% by weight to 100% by weight.

 Next, (c) a catalyst layer is formed on the formed coating layer, and (d) the formed catalyst layer is transferred onto a membrane. The method of transferring onto the film can be performed by heat and pressure by a decal lamination method or a roll lamination method.

Subsequently, (e) removing the base film from the catalyst layer transferred onto the membrane, a catalyst layer having a textured structure having a valley shape on the surface can be formed.

Hereinafter, an electrode for a fuel cell including the catalyst layer will be described.

The electrode for a fuel cell includes an electrode substrate and a catalyst layer formed on the electrode substrate.

The catalyst layer is as described above.

The electrode substrate plays a role of supporting the electrode and diffusing the fuel and the oxidant into the catalyst layer to facilitate the access of the fuel and the oxidant to the catalyst layer.

The electrode substrate may be formed of a conductive substrate, and specifically, a porous film or polymer fiber composed of a carbon paper, a carbon cloth, a carbon felt, or a metal cloth A metal film is formed on the surface of the cloth formed with the metal film), but the present invention is not limited thereto.

The electrode substrate may be water repellent with a fluorine-based resin. In this case, it is possible to prevent the reactant diffusion efficiency from being lowered due to water generated when the fuel cell is driven. Examples of the fluorine-based resin include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxyvinyl ether, fluorinated ethylene propylene (fluorinated ethylene propylene), polychlorotrifluoroethylene, or copolymers thereof.

In addition to the electrode substrate and the catalyst layer, the electrode for a fuel cell may further include a microporous layer for enhancing a reactant diffusion effect in the electrode substrate.

The microporous layer is generally made of a conductive powder having a small particle diameter such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotube, carbon nanowire, nano-horn or a carbon nano ring.

Hereinafter, a membrane-electrode assembly for a fuel cell according to another embodiment will be described with reference to FIG.

4 is a schematic view showing a membrane-electrode assembly (MEA) for a fuel cell according to one embodiment.

4, the membrane-electrode assembly 20 for a fuel cell includes a polymer electrolyte membrane 25 and a cathode electrode 21 and an anode electrode 22 located on both sides of the polymer electrolyte membrane 25 do.

At least one of the cathode electrode 21 and the anode electrode 22 uses the above-described electrode for a fuel cell.

The polymer electrolyte membrane 25 is a solid polymer electrolyte having a thickness of 10 to 200 탆 and has a function of ion exchange for moving hydrogen ions produced in the catalyst layer of the anode electrode to the catalyst layer of the cathode electrode.

The polymer electrolyte membrane 25 is generally used as a polymer electrolyte membrane in a fuel cell, and any polymer electrolyte membrane having hydrogen ion conductivity may be used. Specific examples include a polymer resin having at least one cation-exchange group selected from a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group and derivatives thereof in the side chain.

Specific examples of the polymer resin include fluorine-based polymers, benzimidazole-based polymers, polyimide-based polymers, polyetherimide-based polymers, polyphenylene sulfide-based polymers, polysulfone-based polymers, polyether sulfone- (Perfluorosulfonic acid) (commercially available from Nafion), poly (perfluoro (meth) acrylate, perfluoro (meth) acrylate and the like), poly Carboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, a dehydrofluorinated sulfated polyether ketone, an aryl ketone, poly [(2,2'-m-phenylene) -5,5 '-Bibenzimidazole] [poly (2,2' - (m-phenylene) -5,5'-bibenzimidazole] and poly (2,5-benzimidazole).

Hereinafter, a fuel cell according to another embodiment will be described with reference to FIGS. 5 and 6. FIG.

5 and 6 show an example of the fuel cell, but the present invention is not limited thereto.

FIG. 5 is a schematic view showing the overall structure of a fuel cell according to an embodiment, and FIG. 6 is an exploded perspective view showing a stack of fuel cells according to an embodiment.

5 and 6, the fuel cell 100 according to an embodiment includes a fuel supply unit 110 for supplying a mixed fuel in which fuel and water are mixed, a reforming gas containing hydrogen gas by reforming the mixed fuel, A stack 130 for generating an electric energy by causing a reformed gas containing hydrogen gas supplied from the reforming unit to electrochemically react with the oxidizing agent to generate an electric energy, and a reforming unit 120 for oxidizing the oxidizing agent, And an oxidizing agent supply unit 140 for supplying the oxidizing agent to the anode 130.

The stack 130 includes a plurality of unit cells (not shown) for generating an electric energy by inducing an oxidizing / reducing reaction of a reforming gas containing hydrogen gas supplied from the reforming unit 120 and an oxidizing agent supplied from the oxidizing agent supplying unit 140 131).

Each unit cell 131 refers to a unit cell that generates electricity. The unit cell 131 includes a membrane-electrode assembly 132 for oxidizing / reducing a reformed gas containing hydrogen gas and oxygen in an oxidant, (Or a bipolar plate) 133 for supplying a reforming gas and an oxidant to the membrane-electrode assembly 132. The membrane- The separator 133 is disposed on both sides of the membrane-electrode assembly 132 with the center thereof as the center. At this time, the separator located at the outermost side of the stack may be referred to as an end plate. The membrane-electrode assembly 132 is as described above.

The end plate of the separator 133 is provided with a pipe-shaped first supply pipe for injecting a reformed gas containing hydrogen gas supplied from the reforming unit 120 and a pipe-shaped second supply pipe for injecting oxygen gas And the other end plate is provided with a first discharge pipe for discharging the reformed gas containing hydrogen gas remaining unreacted finally in the plurality of unit cells 131 to the outside, And a second discharge pipe for discharging the remaining oxidizing agent to the outside.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the examples.

Example 1

A PtRu / C catalyst was added in an amount of 0.05 mg / cm < ² > to a solvent in which water and dipropylene glycol were mixed in a weight ratio of 50:50. Asahi kasei, which had a concentration of 15% by weight as an ionomer, Was added in an amount of 37 parts by weight based on the total weight of the anode catalyst layer composition. In addition, water and di-propylene glycol in a solvent mixture in a weight ratio of 50: 50, PtCo / C catalyst to 0.25 mg / cm ² and added in an amount of, and Nafion (Nafion ^® Dupont Co.) of 15 wt% concentration as an ionomer (Asahi Kasei) at a weight ratio of 1: 1 at a concentration of 15% by weight to prepare a cathode catalyst layer composition. At this time, the ionomer was added in an amount of 37 parts by weight based on 100 parts by weight of the catalyst.

On the polyimide base film, fluorinated ethylene propylene (FEP) at a concentration of 11% by weight was coated by a wet method to form a coating layer having a textured structure having a valley shape on the surface. Specifically, the texture structure having a valley shape on the surface of the coating layer is divided into a first region of the top portion and a second region of the valley portion, wherein the thickness of the coating layer in the first region is 1.5 占 퐉 . Then, the anode catalyst layer composition and the cathode catalyst layer composition were coated on the coating layer to form respective catalyst layers. Thereafter, each of the catalyst layers is transferred to both surfaces of the commercial fluorocarbon-based polymer electrolyte membrane by a decal lamination method, and then the base film is removed to form a catalyst coated membrane (CCM) having a textured surface Respectively.

A membrane-electrode assembly was prepared in which an EPL (edge protection layer) film was placed on both sides of a catalyst coated membrane (CCM) formed by bonding the catalyst layer to both sides of a polymer electrolyte membrane, and a cathode electrode and an anode electrode were bound to both surfaces of the polymer electrolyte membrane .

After inserting the membrane-electrode assembly between gaskets, the unit cell was prepared by inserting the membrane-electrode assembly into two separating plates formed with gas channel channels and cooling channels of a predetermined shape.

Comparative Example 1

The anode catalyst layer composition and the cathode catalyst layer composition prepared in Example 1 were each coated on a fluorinated ethylene propylene (FEP) base film and transferred to both sides of a commercial fluorocarbon-based polymer electrolyte membrane to form a catalyst coated membrane (CCM) Thereafter, an EPL (edge protection layer) film was placed on both sides thereof to prepare a membrane-electrode assembly in which a cathode electrode and an anode electrode were bound to both sides of a polymer electrolyte membrane. A unit cell was fabricated in the same manner as in Example 1 using the membrane-electrode assembly.

Evaluation 1: SEM analysis of the catalyst layer

7A and 7B are scanning electron microscope (SEM) photographs of a catalyst layer according to Comparative Example 1 and Example 1, respectively, viewed from above, showing a magnification of 500. FIG. 7A and 7B, it can be seen that the catalyst layer prepared in Comparative Example 1 has a uniform surface and a single region, whereas the catalyst layer prepared in Example 1 has a texture structure in which the surface is divided into different regions .

8A and 8B are scanning electron microscope (SEM) photographs showing side surfaces of the catalyst layers according to Comparative Examples 1 and 1, respectively. 8A and 8B, it can be seen that the surface of the catalyst layer prepared in Comparative Example 1 is flat, whereas the surface of the catalyst layer prepared in Example 1 is a texture structure having a valley shape divided into different regions.

FIGS. 9A and 9B are scanning electron microscope (SEM) photographs showing the height difference on the side of the catalyst layer according to Comparative Example 1 and Example 1, respectively. 9A and 9B, it can be seen that, in the case of the catalyst layer of Example 1, in the surface structure having a valley shape, the first region is formed to have a higher height from the lower surface than the second region, The difference is about 1.5 탆. On the other hand, the height difference in Comparative Example 1 was about 0.1 mu m. It can be seen from this that the surface of the catalyst layer according to one embodiment is formed into a valley-like texture structure having a top portion and a valley portion.

10 is a scanning electron microscope (SEM) photograph of the catalyst layer according to Example 1 taken from above and showing a magnification of 10,000. Referring to FIG. 10, it can be seen that the first region of the top portion in the surface structure of the catalyst layer according to Example 1 has a lower ionomer content than the second region of the valley portion. In this regard, the area covered by the ionomer on the SEM surface was calculated, and as a result, the ionomer content of the first region was five times smaller than that of the second region.

As a result of calculating the area occupied by the first region of the SEM surface, it can be seen that the first region in which the ionomer content is relatively small occupies 30% of the total area of the surface of the catalyst layer.

Also, referring to FIG. 10, it can be seen that the first region having a relatively small ionomer content is porous compared to the second region. In this regard, the porosity of the catalyst layer was measured by the pore size of the surface of the SEM. As a result, it was found that the porosity of the first region was 40 vol% and the porosity of the second region was 10 vol%.

Evaluation 2: SEM analysis of disassociated catalyst layer after electrode evaluation

11A and 11B are scanning electron microscope (SEM) photographs of the catalyst layers disassembled after evaluation of anode and cathode electrodes, respectively, according to Example 1. Fig.

11A and 11B, it can be seen that the catalyst layer after the electrode disassembly manufactured in Example 1 also has a textured structure in which the surfaces thereof are divided into different regions, and specifically, the top portion and the valley portion It can be confirmed that the branch has a texture structure in the form of a valley.

Evaluation 3: Fuel cell performance

The unit cells prepared in Example 1 and Comparative Example 1 were subjected to a non-pressure operation at 65 캜 using H ₂ / air (λ 1.5 / 2.0) as a fuel to evaluate battery characteristics. The results are shown in FIG. 12, and the results are shown for 50% relative humidity and 100% relative humidity, respectively.

12 is a graph showing the results of performance evaluation of the fuel cell according to Example 1 and Comparative Example 1. Fig.

Referring to FIG. 12, when the battery was operated under the condition of relative humidity of 50% and the condition of 100%, in each case, the voltage of Example 1 was higher than that of Comparative Example 1 at the same current density. From this, it can be seen that the fuel cell to which the catalyst layer of Example 1 was applied had better cell performance than that of Comparative Example 1.

10: catalyst layer
12: Lower surface
14: upper surface
20, 132: membrane-electrode assembly
21: cathode electrode
22: anode electrode
25: Polymer electrolyte membrane
100: Fuel cell
110: fuel supply unit
120:
130: stack
131: Unit cell
133: Separator
140: oxidant supplier

Claims (9)

Having a top surface and a bottom surface,
Wherein the upper surface comprises a first region and a second region,
Wherein the first region has a smaller ionomer content than the second region,
Wherein the first region comprises 10% to 50% of the total area of the upper surface. The method of claim 1,
Wherein the first region has an ionomer content 2 to 10 times larger than the second region. The method of claim 1,
Wherein the first region is porous. The method of claim 1,
Wherein the first region has a porosity of 30% by volume to 70% by volume. The method of claim 1,
Wherein the first region and the second region have a height difference from the lower surface. The method of claim 5,
Wherein a height difference between the first region and the second region is 1.0 占 퐉 to 3.0 占 퐉. The method of claim 1,
Wherein the first region is located at a higher level from the lower surface than the second region. A cathode electrode and an anode electrode facing each other; And
And a polymer electrolyte membrane disposed between the cathode electrode and the anode electrode,
The cathode electrode and the anode electrode
Electrode substrate, and
The membrane-electrode assembly for a fuel cell according to any one of claims 1 to 7, which is located on the electrode substrate. A fuel supply unit for supplying a mixed fuel in which fuel and water are mixed;
A reforming unit for reforming the mixed fuel to generate a reformed gas containing hydrogen gas;
A stack comprising a membrane-electrode assembly according to claim 8 and a separator positioned on both sides of the membrane-electrode assembly, wherein a reforming gas containing hydrogen gas supplied from the reforming unit causes an electrochemical reaction with the oxidizing agent to generate electric energy ; And
And an oxidant supply part for supplying the oxidant to the reforming part and the stack.

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